Evidence of polarisation in the prompt gamma-ray emission  from GRB 930131 and GRB 960924

Willis, D. R.; Barlow, E. J.; Bird, A. J.; Clark, D. J.; Dean, A. J.; McConnell, Mark L.; Moran, Lisa; Shaw, S. E.; Sguera, V.

doi:10.1051/0004-6361:20052693

Cited by 92 publications

(55 citation statements)

References 27 publications

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“…For lGRBs, the strong gamma-ray polarization (Coburn & Boggs (2003); Willis et al (2005) but see Rutledge & Fox (2004) and more recently Yonetoku et al (2011)) and a stronger magnetic field in reverse shock (RS) than in forward shock (FS) as a result of a full description of a dozen of lGRBs (Zhang & Kobayashi 2005;Zhang et al 2003;Fan et al 2004;Fraija 2015), have supported the idea that the central engines of lGRBs could be endowed with primordial magnetic fields (Usov 1992;Wheeler et al 2000). In the framework of sGRBs, the question of what field strengths could be reached in a merger remnant before it collapses to a BH has so far remained unanswered, neither evidence of magnetization in the jet has been found.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Early Afterglow in the Short and Hard GRB 090510

Fraija

Lee

Vereš

et al. 2016

ApJ

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The bright, short and hard GRB 090510 was detected by all instruments aboard Fermi and Swift satellites. The multiwavelength observations of this burst presented similar features with the Fermi-LAT-detected gammaray bursts. In the framework of the external shock model of early afterglow, a leptonic scenario that evolves in a homogeneous medium is proposed to revisit GRB 090510 and explain the multiwavelength light curve observations presented in this burst. These observations are consistent with the evolution of a jet before and after the jet break. The long-lasting LAT, X-ray and optical fluxes are explained in the synchrotron emission from the adiabatic forward shock. Synchrotron self-Compton emission from the reverse shock is consistent with the bright LAT peak provided that progenitor environment is entrained with strong magnetic fields. It could provide compelling evidence of magnetic field amplification in the neutron star merger.

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Section: Introductionmentioning

confidence: 99%

Modeling the Early Afterglow in the Short and Hard GRB 090510

Fraija

Lee

Vereš

et al. 2016

ApJ

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“…The RHESSI results highlighted the importance of correctly evaluating the systematic effects, which may mimic a polarisation signature. A recent novel attempt (Willis et al 2005) involved analysing the Earth's albedo flux seen by BATSE for GRB 930131 and GRB 960924, where the lower limits of polarisation were found to be Π s > 35% and Π s > 50% respectively. These figures can only be considered as lower limits due to systematic effects, including natural anisotropies in the Earth's albedo flux and possible limitations in the GEANT 4 code at the time the simulation was run.…”

Section: Introductionmentioning

confidence: 99%

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

McGlynn

Clark

Dean

et al. 2007

A&A

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155

138

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Context. Linear polarisation in gamma-ray burst prompt emission is an important diagnostic with the potential to significantly constrain models. The spectrometer aboard INTEGRAL, SPI, has the capability to detect the signature of polarised emission from a bright γ-ray source. GRB 041219a is the most intense burst localised by INTEGRAL with a fluence of 5.7 ×10 −4 erg cm −2 over the energy range 20 keV-8 MeV and is an ideal candidate for such a study. Aims. Polarisation can be measured using multiple events scattered into adjacent detectors because the Compton scatter angle depends on the polarisation of the incoming photon. A search for linear polarisation in the most intense pulse of duration 66 seconds and in the brightest 12 seconds of GRB 041219a was performed in the 100-350 keV, 100-500 keV and 100 keV-1 MeV energy ranges. It was possible to divide the events into six directions in the energy ranges of 100-350 keV and 100-500 keV using the kinematics of the Compton scatter interactions. Methods. The multiple event data from the spectrometer was analysed and compared with the predicted instrument response obtained from Monte-Carlo simulations using the GEANT 4 INTEGRAL mass model. The χ 2 distribution between the real and simulated data as a function of the percentage polarisation and polarisation angle was calculated for all three energy ranges. The degree and angle of polarisation were obtained from the best-fit value of χ 2 . Results. A weak signal consistent with polarisation was found throughout the analyses. The degree of linear polarisation in the brightest pulse of duration 66 s was found to be 63 +31 −30 % at an angle of 70 +14 −11 degrees in the 100-350 keV energy range. The degree of polarisation was also constrained in the brightest 12 s of the GRB and a polarisation fraction of 96 +39 −40 % at an angle of 60 +12 −14 degrees was determined over the same energy range. However, despite extensive analysis and simulations, a systematic effect that could mimic the weak polarisation signal could not be definitively excluded. Conclusions. Our results over several energy ranges and time intervals are consistent with a polarisation signal of about 60% but at a low level of significance (∼2σ). The polarisation results are compared with predictions from the synchrotron and Compton drag processes. The spectrum of this GRB can also be well fit by a combined black body and power law model which could arise from a combination of the Compton and synchrotron processes, with different degrees of polarisation. We therefore conclude that the procedure described here demonstrates the effectiveness of using SPI as a polarimeter, and is a viable method of measuring polarisation levels in intense gamma-ray bursts.

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“…In GRBs, claims of high polarization (Coburn & Boggs 2003;Willis et al 2005) offer direct measurements of the possibly dominant large-scale magnetic field. If confirmed, these observations argue in favor of magnetic reconnection as the main particle acceleration mechanism.…”

Section: Reconnection In Magnetized Jets Of Active Galactic Nuclei Anmentioning

confidence: 99%

Topics in Microphysics of Relativistic Plasmas

Lyutikov

Lazarian

2013

Space Sci Rev

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Astrophysical plasmas can have parameters vastly different from the more studied laboratory and space plasmas. In particular, the magnetic fields can be the dominant component of the plasma, with energy-density exceeding the particle rest-mass energy density. Magnetic fields then determine the plasma dynamical evolution, energy dissipation and acceleration of non-thermal particles. Recent data coming from astrophysical high energy missions, like magnetar bursts and Crab nebula flares, point to the importance of magnetic reconnection in these objects.In this review we outline a broad spectrum of problems related to the astrophysical relevant processes in magnetically dominated relativistic plasmas. We discuss the problems of large scale dynamics of relativistic plasmas, relativistic reconnection and particle acceleration at reconnecting layers, turbulent cascade in force-fee plasmas. A number of astrophysical applications are also discussed.

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Evidence of polarisation in the prompt gamma-ray emission from GRB 930131 and GRB 960924

Cited by 92 publications

References 27 publications

Modeling the Early Afterglow in the Short and Hard GRB 090510

Modeling the Early Afterglow in the Short and Hard GRB 090510

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

Topics in Microphysics of Relativistic Plasmas

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